What Do Neurons Look Like When They're Growing in the Brain?

Researchers have captured the first-ever picture of newborn neurons in a live brain, according to New Scientist. The photograph was part of a research project conducted by neuroscientists at Columbia University. Published in the journal Neuron, their findings suggest that neuron birth, or neurogenesis, helps mice tell similar experiences apart. This knowledge could someday help us develop new treatments for anxiety, depression, and stress disorders.

Scientists once thought that we were born with all the neurons we’d ever have. Eventually, they learned that certain parts of the brain—particularly the hippocampus, a small region that’s associated with learning and forming new memories—continue making the cells throughout our lifetimes.

Still, researchers had never seen these new neurons form inside a living animal’s body, and they wanted to learn more about how these functioned differently from other brain cells. To answer these questions, Attila Losonczy at Columbia University Medical Center in New York and his colleagues genetically modified mice so that newly formed neurons would glow, and exposed the animals to a variety of stimuli and activities—some frightening, some benign.

Once the mice had formed mental associations with these experiences, the scientists “switched off” the newborn neurons in their brains using a tool called optogenetics, which lets scientists turn cells on and off using light, Science magazine reports. Once they did that, the mice suddenly couldn’t tell the difference between scary stimuli, like a chamber in which they’d received an electric shock, and a separate shock-free chamber. “The finding suggests that newborn cells do something important and special in memory processing, that allows animals to tell apart and separate memories,” Losonczy told New Scientist.

A second experiment yielded the photo of the new neurons. Researchers planted a device with a mini-microscope inside the brains of mice, exposed them to similar—but not identical—stimuli, and watched how the new neurons’ activity compared with mature neurons. They found that the new neurons were “more excitable” than older neurons, which might suggest that they’re better at registering new information than older cells. They also might help keep the firing rate of mature cells low. Since the different cells are encoding similar but separate memories, neurogenesis could help our minds make clear distinctions between different scenarios.

People with panic or anxiety disorders often have trouble telling similar but separate events apart (for example, as New Scientist points out, it might be hard to differentiate between a gunshot and a car backfiring). This could be blamed on a lack of new neurons, experts say. Since depression and schizophrenia also seem to affect neurogenesis, more research into how these baby cells behave might someday help us understand more about these complex psychiatric conditions.